MicroPython Forum (Archive)

A partial solution seems to be the use of Python module io, class BytesIO (see https://docs.micropython.org/en/latest/library/io.html ). The size of the buffer to be allocated can be specified. However, I found no way to clear the buffer other than releasing it using method close and allocate a new ...

Background: an ESP8266 running micropython v1.16, is used to measure the voltage and the frequency of the mains power. The frequency is measured using an ISR, which measures the time it takes to receive 250 pulses. The main loop has been changed from sending the measurements of the voltage and the f...

Ah, now the error messages make sense: in the first case the TypeError was generated when calling micropython.schedule, in the second case the TypeError was generated when calling Frequency.update from within micropython.schedule. Hence the variable number of expected arguments.

The use case is the measurement of the frequency of the mains power supply. The sinus wave form is converted into a square wave. The time T needed to see N rising edges is used to calculate the frequency: f = N/T. The rising edges are counted in an ISR, thus floating point arithmetic is not allowed....

I am not looking for a resolution of about 10 [ns]. Such a resolution is much, much better than I need. The target is to get an accuracy of the measured frequency of 10 [mHz]. This implies that the duration of one period must be measured with an accuracy of 4 [µs]. Given a variation of the ISR laten...

The intent is to build a device which monitors the mains frequency, which is about 50 [Hz] over here. The device should use less than 0.5 [W], which is a reason to use an ESP8266 microcontroller. When the sine wave is converted to a digital signal, the time it takes to receive N pulses needs to be d...

It might look like local versus global variables, but the tests don't support that idea. In the method in which this phenomena was discovered the first line is an assert command containing both cvsp_lst_task and cvsp_max_task in the condition part. Thus the first action on those variables is a read.

Remarkable, this (what seems to be) inconsistent behaviour is thus reproducible in CPython.

The workaround mentioned is now used, so I can continue with development and tests. I probably will go for a shorter module and class name.

The problem described below was found while using the currently latest build of MicroPython on an ESP8266. A (test) class with 3 class variables is created, as well as two instances of the test class. Two class variables are modified, but only one of the two modifications is visible to both instance...

If I understand it correctly, time.time() gets the time from the RTC on the ESP8266, but time.ticks_ms() and time.sleep() use another source for time. I failed to locate the source code of time.time() to verify this statement. Thus the conclusion is that I happen to have an ESP8266 with a very inacc...